scbibner



(No Model.)

TESTING APPARATUS FUR MULTIPLE sw No. 489,099.

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Patented Jan. 3, '1993.

(No Model.)

h 9.9909191999. TESTING APPARATUS POR MULTIPLE SWITCHBOARDS..

UNITED STATES 1 PATENT OEEICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLNOIS, i\SSl(`1rN()lt 'l `O` THE VESTERN ELECTRC COMPANY, OF SAME PLACE.

TESTING APPARATUS FQB MULTIPLE SWITCHBIOARDS.

SPECIFICATION forming part of Lettel's .Patent No. 489,099, dated January 3, 1893.'

Y n Application filed June 19, 1388. Seria1 No.'277,559. (No model.)

To all. it may con/ecrit.l Bejtknoa'rithnt l, CHARLES E. ScRIENER, aitizen of thenited States, residing at Ghicago, 'the county of Cook and, State of Illineis,.i'nyented a certain new and useful Y lmproveinenti'n 'Testing Apparatus for Multiple Swrtchboards, (CaseNo. 173,) of which the following fis a full, clear, concise, and exact description,reference being had to the aene companying drawings, forming a part of this specification- My invention Vis designed to provide ready and etiicient means for determining at one board whether any given line is in use. This I accomplish by connecting the lines at lthe central oice to a cnofrnmon line including a Acurrent generator, by means of which alter- -nating or undulatory direct currents are sent in'derived circuit over the telephone lines, and testing apparatus and circuits seat-ranged that when a connecting plug is inserted in any springjack of a line, the elteet will be indicated to the operator on connecting the test i plug of the testing apparatus with the spring of any other springjaclt switch of the line in use.

In Figure l l have shown three subscribers stations and their lines connected with two multiple switchboards, the lconnecting and testing apparatus being shown at the second board in detail. Fig. 2 is a diagram illustrating the circuits of the telephone lines at the central otiice more in detail, a rotary circuit changing device being shown as apart of the testing apparatus in place of the pendulum g circuitl changing device shown in Fig. l. Fig. 3 is a sectional view of an ordinary loop plug. Fig. 4 is a detailed View of the test plug inserted in a springjack switch so as to bring its tip only in contact with the spring of the switch without lifting said spring from its normal ground contact.

Like parts arc indicated by similar lettersV and numerals et reference throughout the different figures.

lhe metallic circuits of stations l and 3 consist cach of twe branches, one branch extending normally from ground 'at the subscribcrs station through the spring and contact of cathl et the switches et the liuc, and thenccthrtuigh au annunciator to the com- -ot` the line. l connected te a generator f included in a cemmon ground lineincluding the generator, the 4 other branch being norniallypopeu at both ends extending from the subscribers station to the insulated frame or test piece ot each of 5 5 the springjack switches of the line.

The circuit of station 2 consists of a line grounded at the subscribers station and ex-V tending through the' spring and contact of each of the switches of the line at the central 6o ofiice and through an annunciator to the ground line containing the generator. The insulated frames or test piecesot the springjacks of the line connected with station 2 are simply connected together b'y a line grounded 65 at the central oliice. Y l

The only practical difference between Y a grounded circuit, as the circuit of station 2, and a-metallic circuit, as ,the circuit of station 3, is that in one case the circuit is completed 7o through the ground a portion `of the Way, while in the other theentire circuit is metallic.

I will new describe the circuit of station 3 as illustrated in detail in Fig. l. at the ground contact of the telephone switch of station 3, circuit may betraced through the generator and bell over limb ct through the spring and contact of switch b upon the first board; thence through the spring and 8p contact of switch c of the second board and .thence through an annunciator d te the cornmon line e including the generator f. 'lhe other limb g of the metallic circuit of station 3 extends from ,a contact near an upper con- 85 tact point of the telephone switch, through the telephone and thence to the insulated frames or test pieces ef switches b,c. 'lhis limb g, it will be observed, is normally open vat bothends. i On the second switchboard I 9o have shown an ordinary pair of loop plugs 7L and their double `strandediiexible cords, in connection with a listening key h' of wellknown construct-ion. Any two lines may be connepted together in the ordinary manner 95 by inserting the plugs into the springjacks The line u, as above stated, is

mon ground wire c. From dillcrent sides of this generatori provide `branch circuitslto roo different parts el the eoxnmutator or circuit changer et' the testing apparatus In Fig. l

Beginning 1this circuit changer vis designed 'to be operated by apend ulum a' which swings between the terminals'i' and i? of the branches 'i3 and i4 from the different sides of the generator. 5 The penduluinis connected with the circuit k which includes a rheotome and atelephone, the other. terminal of circuitZc beinga test plug k (for detailed view of test plug'k' see Fig. 4). In Fig. l the circuit la is'connected. 1o with the' telephonehy means of an induction coil orconverter k2. As the pendulum vi- 'br'ates the branches 713 and Z4 are alternately n connected withcircuit lc. i. Y.

In Fig. 2, in place ofthe pendulum, I have i5 shown the eccentric Z which is driven, constantly by any suitable means. position shown,branch i3 is open and circuit Za is connected directly with branch 4 through spring Z. The eccentric Z may be in vertizo cal cross section ofthe form shown, cutaway so that only about one half of its circumference will come against spring Z' as the eccentric rotates. Thus during one half the rotation ofV the eccentric Z, connection is made 'hez5 tween circuit k and branch t3 through the 'spring Z' which is,during this time, separated vfrom the contact of brauch 4. During the remaining portion ot its revolution the cut away portion being opposite the spring Z" al- 3o lows spring Z to close upon the contact ot branch '4 whilebran ch @"3 is disconnected from springZ'. Thus the branches t3 and t4 are al- -ternatively connected with the circuit Zu as the eccentric Z is turned.

g5 In'practice the generator f will he construct- 'ed to send alternating or undulatory direct currents over many lines. The current sent over any one line is, therefore, necessarily of low electro-motive force and would not oper- 4o ate a telephone placed directly in the circuit of one of the lines. While the currents sent over the lines by the generator are alternating or undulatory direct the changes in4 strength or direction are, comparatively speaking, gradual as distinguished from abrupt, and these changes take place so slowly that although acting upon the telephone included in circuit even to the extent of causing movements of the diaphragm of the telephone I 5c have discovered that these movements will he of .such character as not to cause auysonnd to one listening. I therefore provide a rheotome or vibrator in the test circuit Za so that the character of the current present may be indicated by the telephone included in said circuit 7c. Y

v In Fig. 2 the plug 7c is shown connected with a' spring of a switch of line a as in the act of testing. As allthe other switches ino fclurled4 in the line a are closed, current will *The sent from generator f to the tip of test plug Zz', thence 'through the telephone and' rheotome included in circuitk to spring Z and i thence by branch fi* to the generator when the 65 eccentricZ is inthevposition shown. When,

however, the eccentric Zis electrically connect- When in the' ed with spring Z' and lifts said spring Z from contact with branch i", the current will be sent from generator fthrough branch 'is to eccentric Z and spring Z'; thence through circuit Zc to the tip of plug k'; thence to the Spring of` the springjack in which test plug k' is inserted and thence over line a tol ground at station 3. The operator listening 4at the telephone will thus hear a const-ant hum or -hiizzin the telephone included in circuit Zc. In case'telephone line awere connected with another line ata spring jack; switchr either Yin front or back otY theswitch in which test plug Za' is inserted, the circuit ot' the generatorl f through circuit 7c would be interrupted ateach turn of the eccentric Z or at each stroke ot the pendulum i. rI"hus, sup` `pose. thespring of switch m lifted -from its contact. The circuit of generator lf'will be found open at said spring of switch 'm and also at the spring Z' when the eccentric is in the position shown. Therefore, during half the revolution of eccentric Z, no current will be sent -through circuit 7c. When, however, contact is formed between eccentric Z and spring Z', the circuit from generatorf may be traced through branch 3 to circuit Za; thence to the test plug la' and thence over line a to groundA at station 3. l/Vith the -line a open thus at switch m back of the switch in which the test plug Zo' is inserted, the derived circuit from generator f will be closed intermittently through the rheotome and telephone in circuit 7c and the operator listen-- ing at the telephone will hear the'h'uin inter` mittently instead of continuously, as is the case when the line a is free. The same effect will be produced in the telephone when a springjack n in front of the one iu which the test plug is insertedis open, butby. means of different connections; that is to say, suppose the spring ot switch n separated from its back contact; current from the generator f would then be sent through the cut oft por- IOO IIO

tion of line a to the tip of test plug 70'; thence through circuit is to spring Z'; thence to branch 4 and thence to the generator with the eccentric-in the position shown. lVhen the spring Z' is .lifted from its contact with branch i4, no current would be sent through the circuit Zo, since though the contact would be complete between branch 'Z3 and the spring Z', still the circuit would be found open at the back contact of switch n. Thus as the eccentric rotates, the circuit of the generator through the rheotome and telephonewould be closed intermittently and the operator listening at the telephone would hear an intermittent hum or buzz. Therefore the operator would know that the line was in use whenever the hum in the telephone should beintcrmittcut, the constant hum or continuous hum, as before den scribed, both indicating that-the line was free. The rate of revolution of the eccentric and of oscillation of thependulum are such that the intermittent hum or buzz caused when the subscrihers telephone is in communication with another, may beheard several times by the operator sending an undulatory direct or alternating current of 10W electromotive force upon said line, a 'test circuit including a telephoneand rheotorne and a circuit changing device for alternately connecting said test circuit with dilerent sides of said generator; whereby, on closing saidtest circuit with any springjack switch of the series the operator listening at the telephone may make a test to determine whether the line is in use. I 2. The combination with the circuit including thc rheotome and telephone connected at one end with the spring of one of thespringjack switches in a telephone line 4and with a circuit changing device at the other end, of a generator current connected with said telephone line to send undulatory direct or alternating currents thereon and branch circuits from diilfcrent Sides of said generator to the circuit changing device; whereby it may be .determined whether the tclcphoncline is conr uected or in use, Substantially as and for the purpose specified.

3. The combination with several telephone Alines connected each through a different series of springjack switches to acommon ground line4 including a generator, of a testing apparatus which is alternatively connected' to different sides of said generator at one end and provided with a test plug at the other end for connecting with a springjack switch 'of any one of the lines; whereby it may he determined by listening at-the telephone of the tes'tinor apparatus when the test" plug is connected 4with a' 'spring of any telephone line,4 whether said line is open at any other of its series of springjack switches, substantially as and forthe purpose specified.

4. The combinationwith a telephone line extending through a series of switches, of a currentl generator connected with said line for sending slowly changing alternating or unT dulatory direct currents over said lines, a rheotome, a circuit changing device, and a telephone, whereby the presence ofisaid currents will be indicated only when the rhectome is connected in circuit with said telephone.

In witness whereof I hereunto subscribe my naine this 15th day of June, A. D. lSSS.

. CHARLES E. SCRIBNER. Witnesses:

Gnouen i). BARTON,

tHAs. C. WOODWORTH. 

